Determination of the molecular weight between cross‐links of elastomeric stocks by tensile retraction measurements I. SBR vulcanizates

Tensile retraction measurements were used to determine the effective molecular weight between cross‐links of vulcanized SBR rubbers. The procedure has proven to be a rapid, precise, and reproducible method of obtaining the total number of effective cross‐links present in an unperturbed elastomer. Since the only data needed besides stress‐strain curves were the sample density and the volume fraction of filler present, questionable evaluation of unknown constants was avoided. In addition, an indication of the interactions between the polymer and filler can be studied. Such a relationship with hydrocarbon rubbers appears to give information that will directly relate to end use applications.